Tuesday, 26 June 2012

Telemotor control

Telemotor control
Telemotor control
Telemotor control is a hydraulic control system employing a transmitter, a receiver, pipes and a charging unit. The transmitter, which is built into the steering wheel console, is located on the bridge and the receiver is mounted on the steering gear. The charging unit is located near to the receiver and the system is charged with a non-freezing fluid.

Figure 12.3 Swash piate pump

1 Steel ball
2 Pump body
3 Tilt box (swash plate)
4 Cylinder block
5 Valve plate
6 Mainshaft
8 Oil seal housing
9 Gland housing
10 Retracting plate
11 Piston
12 Bridge piece
13 Plunger
14 Spring
15 Case nuts and bolts
16 Shaft sleeve
17 Needle bearing
18 Roller journal
19 Oil seal
20 Retaining plate
21 Slipper
22 Circlip
23, 24 O-rings
26 Vent plug
27 Roller bearing cap
28 Control lever
29 Oil seal
30 Top trunnion and cover
32, 34 Bottom trunnion and cover
The telemotor system is shown in Figure 12.4. Two rams are present in the transmitter which move in opposite directions as the steering wheel is turned. The fluid is therefore pumped down one pipe line and drawn in from the other. The pumped fluid passes through piping to the receiver and forces the telemotor cylinder unit to move. The suction of fluid from the opposite cylinder enables this movement to take place. The cylinder unit has a control spindle connected to it by a pin. This control spindle operates the slipper ring or swash plate of the variable delivery pump. If the changeover pin is removed from the cylinder unit and inserted in the local handwheel drive then manual control of the

steering gear is possible. Stops are fitted on the receiver to limit movement to the maximum rudder angle required. The charging unit consists of a tank, a pump, and shut-off cocks for each and is fitted in the main piping between the transmitter and receiver.
In the transmitter a replenishing tank surrounds the rams, ensuring that air cannot enter the system. A bypass between the two cylinders opens as the wheel passes midships. Also at mid position the supercharging unit provides a pressure in the system which ensures rapid response of the system to a movement of the wheel. This supercharging unit also draws in replenishing fluid if required in the system, and provides a relief valve arrangement if the pressure is too high. Pressure gauges are connected to each main pipeline and air vent cocks are also provided.
In normal operation the working pressure of about 20 to 30 bar, or the manufacturer's given figure, should not be exceeded. The wheel should not be forced beyond the 'hard over' position as this will strain the gear. The replenishing tank should be checked regularly and any lubrication points should receive attention. Any leaking or damaged equipment must be repaired or replaced as soon as possible. The system should be regularly checked for pressure tightness. The rudder response to wheel movement should be checked and if sluggish or slow then air venting undertaken. If, after long service, air venting does not remove sluggishness, it may be necessary to recharge the system with
new fluid.

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